During the pandemic, many institutions shifted to online teaching, and in some cases, this included existing peer learning programs. As the pandemic receded, some of these peer learning programs returned to face-to-face operation and others adopted a blended format, while others remained online. Interestingly, the literature suggests that online peer learning is somewhat more effective than face-to-face peer learning. This might be because online peer learning enables responses at any time (which might be more thoughtful), anonymity, and a wider nexus of relationships, although it can create issues regarding the initial development of trust. There are a great many studies of both face-to-face and online peer learning, but relatively few that directly compare both. By way of addressing this gap, this paper aims to systematically review 17 papers that directly compare both, informed by and updating the only previous review in this area. Online performs better than offline learning in terms of cognitive outcomes, with a small to moderate effect size. However, the associated socio-emotional issues are more complex. Online learning offers flexibility regarding response time, but sacrifices the immediate dialogue of offline learning. Some cultures found accepting peer learning more difficult. Few studies undertook longer-term follow-up, although with more practice motivation, this might well improve. The results have implications for the type of peer learning chosen by pedagogical designers as appropriate to their own learning context.